public class Fraction {
    public static void main(String[] args) {
        //int num = 1;
        int i = 1;
        double sum = 0;
        while(i <= 100) {
            int flag = i;
            if(flag % 2==0){
                flag = -1;
            }else{
                flag = 1;
            }
            sum += (flag) * (1.0/i);
            i++;
        }

        System.out.println(sum);
    }
}
